This is just my opinion, but guys are probably less likely to come rolling home drunk at 2 a.m. with lipstick on their box shorts if mom or the mother-in-law is living there.
Lipstick on the boxers? What the...???
ROTFLOL How would in-laws see lipstick on boxers; I think that's getting very personal if they keep pulling the guys pants down to check him out. I suppose they're also pulling the pants up in the morning with the snugness test mom's use to see if the boy needed a new pair of pants.
Well, I suppose that sort of attention would keep everyone in line. Best to be sober minded and monogamous to begin with, or else Momma's gonna check your drawers.